The present invention generally relates to fluorescent lighting fixtures, and more particularly relates to techniques for optimizing the efficiency of fluorescent lighting fixtures by optimizing the cold spot temperature of the fixture's fluorescent lamps. The present invention has particular applicability to indirect and direct/indirect fluorescent lighting fixtures using compact fluorescent lamps such as T5 and T5HO lamps, collectively referred to herein as T5 lamps.
It is well known that T5 fluorescent lamps operate at their greatest efficiency when the cold spot of the lamp at the end of the fixture is at approximately 45° C. In open fixtures, such as totally indirect fixtures, the lamp's cold spot generally runs below the optimum temperature, typically about 38° C. to 40° C. In these types of fixtures, special sleeves have been devised to increase the lamp's cold spot temperature to a temperature closer to the optimum operating temperature. However, in other types of fixtures, such as multi-lamp wall wash T5 fixtures and down light T5 fixtures, the cold spot of the lamps generally runs at a temperature that is higher than the optimum operating temperature. For example, it has been found that in certain multi-lamp T5 wall wash fixtures, the cold spot of the lamps will heat up to about 55° C. In these types of fixtures, the normal operating temperature of the T5 lamps is elevated because the lamps of the fixtures are normally closer together, and because the heat generated by the lamp normally is trapped within the fixture. Thus, in these types of fixtures, heat needs to be extracted from the cold spot end of the lamp in order to bring the cold spot temperature down, if the lamps are to be run at optimum efficiency. On the other hand, the heat extraction should not be so great as to excessively lower the lamp's temperature beyond its optimal operating temperature.
A need therefore exists for a means for lowering the cold spot temperature of fluorescent lamps, such as T5 fluorescent lamps, in fluorescent lighting fixtures where the construction of the lighting fixture and the configuration of the lamps causes the cold spot temperature of the lamps to rise above the lamps' optimum operating temperature. A need also exists for a means for lowering the cold spot of the lamps in such fixtures only by the degree necessary to achieve optimum operating temperatures. Since such needs often arise in lighting fixtures using two or more fluorescent lamps grouped closely together a need also exists for a means for efficiently extracting heat from such groups of lamps.